Coccidioidomycosis is caused by infection with Coccidioides immitis or C. posadasii. Coccidioides immitis and C. posadasii are the fungal etiologic agents of coccidioidomycosis (aka Valley Fever) and are endemic to arid soils of the southwest United States, as well as parts of Mexico, and Central and South America. Primary hosts acquire Coccidioides via inhalation of aerosolized arthroconidia upon soil disruption. Coccidioidomycosis most commonly causes a progressive pulmonary infection in humans and other vertebrate hosts but also can disseminate to other body parts including the skin, brain, bone, and meninges. This disseminated secondary coccidioidomycosis often is severe and can result in patient death (See Reference 3). However, in cases where infection is resolved patients usually acquire a specific and lifelong immunity to the fungus.
Coccidioidomycosis infection rates have increased dramatically in the last decade with the state of Arizona documenting the number of reported cases per 100,000 people having increased from 20.8 in 1997 to 86.1 in 2006. A potential causes for this increase include influxes of immunologically naïve individuals into Arizona. A significant number of individuals from outside the Coccidioides endemic region migrate annually to the desert southwest and are at greater risk for development of coccidioidomycosis, even after return to their respective homes. These infections, therefore, are likely to escape or confound diagnosis in non-endemic regions.
While Real Time PCR based assays have been developed that help clinicians identify Coccidioides as a cause of illness, these assays do not accurately quantify the load of Coccidioides organisms in an infection. Population influx in Coccidioides-endemic areas may contribute to rate of infection increases not only because there are additional individuals relocating to these areas but also because there is increased new home construction in virgin desert areas, and subsequent soil disturbances.